Medical personnel, such as orthopaedic physicians and physical therapists, have long sought an effective way to measure in isolation the strength of the musculature of a patient's lower back in rotation about a vertical axis. Medical personnel have also sought a machine which could be used for the rehabilitation of the musculature of a patient's lower back after surgery, a stroke or other illness, or an accident, whereby the patient could rotate his or her lower back musculature to its full strength capability and range of motion without danger of injury.
Also, employers who employ persons in job functions which require extensive rotational movement of the lower back musculature have long sought a way to screen potential employees for rotational strength deficiencies or rotational range of motion limitations. By testing the rotational strength of a potential employee's lower back musculature prior to assigning the person to the specified job function, the employer can determine whether the potential employee has the lower back musculature rotational strength and rotational range of motion needed for the job function. Such industrial screening is of value in keeping health insurance costs down by reducing the incidence of employee injuries, and is also of value by increasing work-force productivity.
In order to effectively measure in isolation the strength of the musculature of a patient's lower back in rotation about a vertical axis, it is necessary to prevent muscle groups in the patient's upper and lower body, other than those muscles in the lower back, from participating in the rotational movement during the test, rehabilitation or exercise procedure. These extraneous muscle groups, such as muscles in the pelvic area, legs, shoulders and arms, must be adequately stabilized if the rotational strength of the musculature in the lower back is to be effectively measured in isolation during the test, rehabilitation or exercise procedure. Also, the patient's lower back musculature range of rotational motion cannot be determined unless these extraneous muscle groups are prevented from taking part in the rotational movement.
Securing the upper and lower body of the patient by use of belts alone is not sufficient, because belts are not rigid enough to provide the degree of stabilization required. Further, the stabilization provided by belts alone is not reproducible, i.e., it cannot be guaranteed that the patient will be stabilized in the same way for each individual test, rehabilitation or exercise procedure. Further, stabilization by belts alone often causes discomfort or pain to the patient. Any major discomfort or pain to the patient during the test, rehabilitation or exercise procedure inhibits the patient in his or her rotational movement, producing inconsistent measurements of the strength of the musculature in the lower back and of the rotational range of motion.